[iOS] Grant media capabilities to the WebContent and GPU processes during capture and playback
<rdar://problem/116242683>
Pull request: https://github.com/WebKit/WebKit/pull/21113
Committed 271761@main (7b6ea0137423): <https://commits.webkit.org/271761@main> Reviewed commits have been landed. Closing PR #21113 and removing active labels.